1. Field of the Invention
The present invention relates to a control apparatus for a hybrid vehicle for driving a combustion engine and an electric motor, and in particular, to a control apparatus for a hybrid vehicle that increases the temperature of water in the engine, which relates to the temperature of the engine itself, when the vehicle is cruising.
This application is based on Japanese Patent Application No. 11-288751, the contents of which are incorporated herein by reference.
2. Description of the Related Art
Conventionally, hybrid vehicles which carry electric motors as power sources for driving the vehicles in addition to engines are known.
In the conventional hybrid vehicles, there are parallel hybrid vehicles which use motors as assisting driving sources for assisting the output from the engines. The parallel hybrid vehicle assists the output from the engine by the motor when the vehicle accelerates, charges a battery by deceleration regeneration when the vehicle decelerates, and performs various controls, to respond the driver""s demands while maintaining the remaining charge of the battery (as disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 7-123509).
To improve the fuel consumption of the conventional hybrid vehicle, gear ratios are made so high that the vehicle can travel at a low engine speed to increase energy regenerated by the motor, and an idling stop mode is provided so that, when the hybrid vehicle is stopped, the engine is stopped or the period for which the fuel supply to the engine is stopped is extended. Therefore, the temperature of the water in the engine is rises with difficulty, and the performance of a heater using the water temperature of the engine for air conditioning in the vehicle may be degraded.
It is therefore an object of the present invention to provide a control apparatus for a hybrid vehicle which can improve the performance of the heater by quickly increasing the temperature of the water in the engine even in a cruise mode in which the vehicle is traveling by the driving force produced by the engine without assistance by the motor.
In a first aspect of the present invention, a control apparatus for a hybrid vehicle is provided with a combustion engine (E) for outputting a driving force, an electric motor (M) for generating a force for assisting the output from the engine, and a power storage unit (battery 22) for storing electric energy generated by the motor acting as a generator using the output from the engine and electric energy regenerated by the motor when the vehicle decelerates. The control apparatus comprises: an engine temperature measuring device (steps S401, S402, and S407) for measuring the temperature of the engine, and a generated energy increasing device (step S409) for increasing the energy generated by the motor acting as a generator when the vehicle is traveling by the driving force from the engine without the assistance of the motor, and when the engine temperature measuring device determines that the temperature of the engine is equal to or below a predetermined temperature.
According to the control apparatus for the hybrid vehicle, in a cruise mode in which the vehicle is traveling by the driving force from the engine without the assistance of the motor, the energy generated by the motor is increased, and the charging current is supplied to the power storage unit, causing the Joule heat due to the internal resistance of the power storage unit, which warms the power storage unit. Further, the load on the engine due to the generation is increased, thereby quickly increasing the engine water temperature.
In a second aspect of the present invention, the engine temperature measuring device comprises: an intake air temperature measuring device (step S401) for measuring the temperature inside an air intake passage in the engine (intake air temperature TA); an outside air temperature calculator (step S402) for calculating the temperature outside the vehicle (outside air estimated temperature TAFCMG); and an engine water temperature measuring device (step S407) for measuring the temperature of water in the engine (engine water temperature TW).
The control apparatus for the hybrid vehicle increases the energy generated by the motor, when the intake air temperature measuring device determines that the temperature inside the air intake passage is equal to or below a predetermined temperature (battery/heater warming determination execution lower limit temperature #TABWARM), when the outside air temperature calculator determines that the temperature outside the vehicle is equal to or below a predetermined temperature (battery/heater warming determination execution lower limit estimated temperature #TAHWARM), or when the engine water temperature measuring device determines that the temperature of water in the engine is equal to or below a predetermined temperature (battery/heater warming determination execution lower limit water temperature #TWBWARM).
In a third aspect of the present invention, the control apparatus for the hybrid vehicle further comprises: a remaining charge measuring device (battery ECU 13) for measuring the remaining charge of the power storage unit; and a generation regulating threshold value corrector (step S302) for increasing a threshold value for regulating the generation by the motor when the generated energy increasing device increases the energy generated by the motor (step S303), the threshold value being set depending on the remaining charge measured by the remaining charge measuring device.
When it is determined that the power storage unit is over-charged while the engine water temperature is sufficiently high, the generation by the motor is prohibited, and the power storage unit is not further charged. When the generated energy increasing device increases the generated energy in order to increase the engine water temperature, the generation regulating threshold value of the remaining charge for stopping the generation by the motor is increased so that the charging of the power storage unit is continued. The charging current causes the Joule heat due to the internal resistance of the power storage unit, which warms the power storage unit. Further, the load on the engine due to the generation is increased, thereby quickly increasing the engine water temperature.
In a fourth aspect of the present invention, the control apparatus for the hybrid vehicle further comprises: a voltage variation detector (battery ECU 13) for detecting a variation in the voltage of the power storage unit; and an ignition timing retarding (delaying) device (FIECU 12) for retarding (delaying) an ignition timing in the engine when the remaining charge exceeds the threshold value (SOC2) and reaches the fully-charged state, or when the voltage variation detector detects a predetermined variation of the voltage.
When the power storage unit is fully charged, that is, when the power storage unit cannot receive any charging current, the engine water temperature is increased by retarding the ignition timing in the engine so as to reduce the combustion efficiency. This increases the temperature of the heater, and the power storage unit can be warmed by the fans of the heater. As the power storage unit is warmed, the amount of assistance and the amount of regeneration by the motor M can be quickly increased, thereby improving the fuel consumption.